Longquan Xu

Self-assembled enzyme–inorganic hybrid nanoflowers and their application to enzyme purification

We report a novel method to synthesize organic-inorganic nanoflowers for crude soybean peroxidase (SBP) purification. A hierarchical flower-like spherical structure with hundreds of nanopetals was self-assembled by using crude SBP as the organic component and Cu3(PO4)2·3H2O as the inorganic component. The structure of the hybrid nanoflowers was confirmed by Fourier-transform infrared spectroscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy, and the enzymatic activity of SBP embedded in the hybrid nanoflowers was evaluated using guaiacol as substrate. Compared with free crude SBP in solution, SBP embedded in hybrid nanoflowers exhibited enhanced enzymatic activity (∼446%). The hybrid nanoflowers also exhibited excellent reusability and reproducibility during cycle analysis. These results demonstrate that synthesis of hybrid nanoflowers is an effective enzyme purification strategy.

Hierarchical assembly of enzyme-inorganic composite materials with extremely high enzyme activity

We have synthesized a novel composite material with a hierarchical flower-like structure and extremely high enzyme activity. The spherical, hierarchical flower-like structure with numerous small flowers was formed through self-assembly using papain as the organic component and Cu3(PO4)2·3H2O as the inorganic component. This hybrid-nanoflower structure was confirmed by Fourier transform infrared spectroscopy, and X-ray diffraction. The enzyme activity of papain embedded in the hybrid nanoflowers was further evaluated using BAEE as a substrate. Compared with free papain in solution, the hybrid materials exhibited extremely high enzyme activity (∼4510%). A study on the relationship of enzyme weight percentage and pattern structure with enzyme activity revealed that enzyme activity was mainly affected by the material structure. These results demonstrate that this hierarchical structure can effectively increase enzyme activity.

Synthesis and investigation of a novel luminous hydrogel

A novel europium-containing luminescent hydrogel was designed and synthesized through free radical copolymerization and ester hydrolysis. A Eu-organic complex containing polymeric reactivity groups (Eu(DBM)2(Phen)(MA)) was synthesized and polymerized with vinyl acetate (VAc). Then, the obtained polymer poly (VAc-co-Eu(DBM)2(Phen)(MA)) was hydrolyzed to become Eu-containing poly (VA-co-Eu(DBM)2(Phen)(MA)) under alkaline conditions. Eu-containing poly (VA-co-Eu(DBM)2(Phen)(MA))s were prepared with different proportions of Eu3+, and their spectroscopic properties were investigated in detail. Polymer films with the optimum composition exhibited narrow fluorescence emission, hydrophilic properties, good thermal stability (Td: up to 232 °C), and solvent resistance after cross-linking.

A novel transparent luminous hydrogel with self-healing property

Intelligent hydrogels have promising applications in a wide variety of fields. Herein, a transparent luminous hydrogel with self-healing properties was prepared from a novel Eu-containing PVA that was designed and synthesized via free radical copolymerization and ester hydrolysis. Fluorescence behavior of the Eu-PVA hydrogel depended on the Eu organic complex in Eu-PVA. The water content of the hydrogel depended on the concentration of the PVA water solution. The strength of the Eu-PVA hydrogel was affected by the concentration of the cross-linking agent (boric acid) and the content of Eu-PVA. Eu-containing organic complex, which had good UV photoluminescence, was stabilized in hydrogels without diffusion. The spectroscopic properties of the Eu-containing polymers were investigated in detail. Moreover, the Eu-PVA hydrogel exhibited strong visible fluorescence and excellent self-healing properties. Furthermore, the Eu-PVA hydrogel had excellent biocompatibility since mouse osteoblasts could grow well on its surface. The approach in this study provided new insights into the design and fabrication of multifunctional intelligent soft materials for biomedical applications.

Synthesis and investigation of an erbium-containing photosensitive polymer

Er organic complexes are generally used in polymer-based optical amplifiers by doping. This study presents a method for creating an Er-containing photosensitive polymer by free radical copolymerization. Two types of Er organic complexes containing polymeric reactivity groups were synthesized and investigated. Er(TTA)2(Phen)(MA), which has high photoluminescence, was polymerized with glycidyl methacrylate (GMA) for use as a novel UV-written polymer material. Poly(GMA-co-Er(TTA)2(Phen)(MA) was prepared with different proportions of Er, and its spectroscopic properties were investigated in detail. Polymer films with the optimum proportion (the molar ratio of GMA and Er(TTA)2(Phen)(MA) was 115 : 1) exhibited good UV-light lithographic sensitivity, narrow near-infrared luminescence, good thermal stability (Td: up to 303 °C), and solvent resistance after crosslinking. Micropatterns with smooth top surfaces were fabricated from the resulting polymer by direct UV exposure and chemical development.

A novel high-strength polymer hydrogel with identifiability prepared via a one-pot method

Obtaining high strength hydrogels with good biocompatibility and identifiability is a challenging task. Herein, a new approach is presented that enables the simple one-pot synthesis of a high strength polymer hydrogel on the basis of silicone, poly(hydroxyethyl methacrylate) (PHEMA) and an Eu(III) organic complex. The composition and properties of the hydrogel could be easily tuned because of the good solubility of the monomers and non-interfering polymerization processes. The hydrogel exhibits an excellent integrated performance with toughness, high resilience, biocompatibility, and identifiability.

Multiscale immobilized lipase for rapid separation and continuous catalysis

Enzyme–inorganic hybrid nanoflowers have drawn extensive research interest for enzyme immobilization owing to their enhanced enzymatic activity, high surface area, and excellent chemical stability. However, their low mechanical stability and challenging separation hinder their application. Herein, we report a facile and effective strategy to construct nanoflowers–PVA–chitosan composite (NPC) hydrogels that have excellent mechanical strength, high catalytic activity, and are easy to separate. Lipase–Cu3(PO4)2·3H2O nanoflowers were uniformly immobilized in hydrogel networks, and the substrate and the product can travel freely. The excellent mechanical properties of the hydrogels effectively protect the fragile nanoflowers from external stress, ensuring enzyme activity. Compared with free lipase (97.28 U g−1), NPC3 exhibited a higher enzymatic activity (146.12 U g−1) at 37 °C and pH 7.4. Furthermore, hydrogels as bulk materials can be processed into various physical forms, such as thin films and spheres. The product can easily flow out without the need for a separation process. It is expected that this immobilization method would have great potential in industrial catalysis.

Studies on antioxidant activity of teasaponins after hydrolyzed by enzyme

The biological activity of teasaponins and their molecular structure are closely related, and the activity of saponins may be increased with the change of their molecular structure. In this report, teasaponins were hydrolyzed by Aspergillus niger for increasing the antioxidant activity. The antioxidant activity of teasaponins before and after hydrolyzed was tested by DPPH, and the result showed four new teasaponins were produced after hydrolysis, and their antioxidant activity was increased significantly than the original teasaponins before hydrolysis, the radical scavenging capacity (RSC) was partly up to 95 %.

Purification of soyasaponin -β-galactosidase from Aspergillus sp.39

In order to increase physiological activity of soyasaponin, enzyme hydrolysis of soyasaponin was studied. The enzyme which hydrolyzes soyasaponin to lower sugar soyasaponin was obtained from Aspergillus sp.39s. And it was purified by the method of biologic chromatography system. The method of SDS-polyacrylamide gel electrophoresis was used to determine the molecular weight of the enzyme produced by Aspergillus sp.39s. The molecular weight was about 50 kDa. The optimum pH and temperature of soyasaponin-β-galactosidase produced from sp.39s was 5.0 and 40°C respectively. Soyasaponin-β-galactosidase was comparatively stable in the pH range from 3.0 to 7.0 and in the temperature range from 20°C to 60°C.